1. Field of the Invention
The present invention relates to the design of integrated circuits; and, in particular relates to the design of integrated circuits for audio applications, such as audio amplifiers.
2. Discussion of the Related Art
In an audio system, the speakers are driven by audio amplifiers. Without special measures to provide a gradual turning on or turning off of such audio amplifiers, audible sounds, commonly known as "clicks" and "pops," can result. These sounds are not only acoustically unpleasant, the current associated with clicks and pops can damage the speakers. Thus, an audio system using an integrated circuit audio amplifier typically provides components external to the integrated circuit to avoid clicks and pops. Such external components cannot be easily integrated into the audio amplifier, since they typically include large capacitances which cannot be practically provided on the integrated circuit. These external components also occupy valuable board space and increase system cost. Thus, there is a need to minimize the external components necessary for avoiding clicks and pops.
An integrated circuit audio amplifier, however, provides an input pin for connection of a bypass capacitor to a DC reference voltage ("half-supply") between a power supply V.sub.dd and a power supply V.sub.SS. Such a bypass capacitor protects the integrated circuit from undesirable effects of noise in the power supplies.